Lecture 6 - Muscle Dynamics Flashcards
A limb is an ____ system. Explain.
inertioviscoelastic;
mass, elasticity, viscosity all mater
The force-length relation of a muscle depends on…
- innervation
- velocity
When does a muscle exert the most force?
when it is stretched (spring), AND increasing innervation (adjusting rest length and stiffness) increases stretch!
Strong innervation vs no innervation: where does the strong innervation graph peak?
at the zero-innervation rest length (1.0)
myosin & actin overlap perfectly
In innervation graph, ___ is standardized. In velocity graph, ___ is standardized.
length (/zero innervation rest length);
force (/isometric force)
how is muscle force related to the velocity (rate at which length is changing)?
- The faster muscle is shortening, the less force you get
- bigger force when muscle is longer
- max force when muscle just begins to stretch longer
equalibrium position
the position where a body part would stay still given the current innervation
equalibrium-point theory of motor control
when you want to move hand from A -> B, you se the innervations ofyour arm muscles to make their equilibirum position = B
supposed to be automatic movement caused by viscoelasticity of muscles, brain does not need to compute path or innervations en route
evidence against equalibrium-point theory
when you push arm towards target, it drifts back instead of continuing onwards
the brain exploits ____ to increase force output. Example?
muscle dynamics;
crouch before jump, even if starting from crouched position. This lengthens knee extensor muscles.
muscles are controlled to maximize ___ and ___.
Force & power
power peaks at ____ max contraction velocity
30%
Power is affected by which variables?
Force x velocity
example of a case where we maximize power
When biking, we switch gears to keep muscles around 30% max contraction velocity (range of max power)
